The present invention relates to a tag for use with a personnel monitoring system. More particularly, the invention relates to a tag for use with a house arrest or other monitoring system wherein individuals who wear the tag can be monitored for compliance with orders or instructions to remain at a prescribed location. Even more particularly, the present invention relates to such a tag that includes anti-tamper circuits therein so that any attempt to remove the tag can be detected and signaled to a central monitoring location.
To illustrate a potential application of a personnel monitoring system, reference is made to a newspaper article appearing in the Los Angeles Times on Wednesday, Sep. 12, 1985, Part I, page 3. The article indicated that on Tuesday, Sep. 10, 1985, U.S. District Judge Terry J. Hatter, Jr. sentenced David Alan Wayte to spend "six months under house arrest at his grandmother's home for failing to register for the military draft." While this was reported as "one of the most unusual sentences in recent memory," it is believed to represent a major trend for future sentencing of non-violent offenders. This is particularly evident in view of the ever overcrowded prisons and jails that exist in every jurisdiction across the U.S. and throughout the world. House arrest thus represents a very significant and viable alternative to conventional incarceration of convicted law breakers, especially those found guilty of non-violent crimes.
While those sentenced to house arrest will generally recognize the need and benefit of complying with the sentence imposed, there nonetheless remains the need to monitor the presence or absence of such individuals to ensure that the sentence imposed is being followed so that justice can be satisfied. For example, in the instance cited above, the attorneys for the convicted individual, David Wayte, wanted the judge to impose community service work as punishment. While community service may be a very appropriate sentence to impose in some instances, the judge felt that because Mr. Wayte was already doing community service on a regular basis, a sentence of house arrest should be imposed to punish Wayte by not allowing him to perform such service. Hence, if Wayte were to violate his sentence by leaving his grandmother's house without the knowledge of the court, the purposes of Judge Hatter's sentence would be frustrated.
While monitoring the presence or absence of a single individual at a prescribed location may seem like an easy task, it really is not. Moreover, where there are a large number of individuals who must be monitored, each at a different "house-arrest" location, the problem becomes exceedingly more complex, especially where some of the individuals may not want to fully comply with the need to wear the tag at all times. Hence, there is a need in the art for a system that can efficiently and accurately monitor the presence or absence of a large number of individuals who have been sentenced to remain at specific locations under house arrest. Advantageously, such a system could also be used to monitor the presence or absence of those individuals on parole, i.e., those individuals who are more or less free to move about as they want during certain hours of the day, but who must "report in" at specified locations at specified times. There is a further need to provide a tag that can be comfortably worn by those individuals being monitored but that can not be removed or tampered with without being detected.
The present invention meets this need by providing an electronic monitoring system that inexpensively and accurately monitors the house-arrest location of a large number of individuals at a wide variety of different locations. Moreover, such monitoring is accomplished in a way that is not readily noticeable to those persons with whom the monitored individuals come in contact at the house-arrest location, and in a way that is essentially tamper-proof and secure, with suitable alarm messages being promptly given at a central monitoring location in the event that anything out of the ordinary is sensed at a given house-arrest location.
Electronic monitoring systems used to determine and monitor the location of individuals are known in the art. The concept of such electronic personnel monitoring systems probably existed long before the technology was available to realize them. Fictional accounts have long referred to the concept of an electronic personnel monitoring system (e.g., the "Spider Man" comic strip). Numerous press reports have also broadly discribed the benefits of such systems, but have not disclosed the technology for how such systems could be realized, other than in the broadest of terms.
In Schwitzgebel, et. al., U.S. Pat. No. 3,478,344, there is disclosed a prisoner monitoring system that keeps track of the location of prisoners within a specified boundary. This is accomplished by a system that uses RF transmitters, mounted on the wrist of the prisoner being monitored, and an array of directional antennas that can determine the location of a transmitter with respect to the antenna array. The wrist RF transmitter is powered by a battery pack worn on the prisoner's belt. Two batteries are employed so that the unit remains powered if one battery is removed. The wrist band includes a conductive wire therein that, if broken or cut, is used to signal that the wrist band has been improperly removed.
While the system disclosed in Schwitzgebel may have represented an important advance in the art at the time it was made (1965), there are many reasons why the system disclosed in Schwitzgebel may not provide a viable house arrest system for use today. For example, the large battery pack is unsightly and is cumbersome for the prisoner to wear. The antenna array that must be placed around the premises is likewise unsightly and draws attention to the fact that the location is being monitored. Moreover, the conductive wire check of the wrist band could be easily circumvented if a prisoner wanted to remove the device without being detected. Further, external RF signals could easily interfere with the intended RF signal, or external RF signals could be beamed into the monitored area by an outside accomplice in order to "jam" the system.
In Mandel, U.S. Pat. No. 3,898,984, an ambulatory patient monitoring system is disclosed. A telemetry system using a single RF frequency for each individual to which the system is attached monitors critical body functions. FM modulation is used. A transponder unit worn by the individual is triggered by an interrogating signal, in response to which interrogating signal selected information about the individual, as sensed by special sensors on the individual, is transmitted to a receiver. In this way, the receiver is able to monitor certain body functions of the patient being monitored. However, location information about the patient is not included in the transmitted information.
In DePedro, U.S. Pat. No. 3,882,277, electrocardiograph information is telemetered from a patient to a telephone transmission link system that carries the information to a central monitoring location. Thus, a combined telemetry and telephone transmission system is employed to monitor physiological signals. However, as disclosed, such physiological signals do not include the location of the patient being monitored.
In the UK Patent Application of Anders et. al., GB2141006A, a system is disclosed that measures location, identification, or motion. The system therein described uses "passive" tags that may be placed on movable objects. The location of any of these movable objects may be ascertained through a system that uses active transceivers to interrogate the passive tags. In response to such interrogation, the passive tags transmit an identification code. The location of the tag is sensed through the use of multiple antennas spaced at predetermined intervals, or through repeater-relay transceivers spaced at predetermined intervals, around the area being monitored.
From the above it is seen that the prior art teaches electronic monitoring systems that monitor the presence or absence of individuals from a prescribed location and/or specified parameters of an individual at remote locations. To accomplish such monitoring, it is known to use tags worn by movable objects or individuals, RF telemetry to and from such tags, repeaters, and telephone transmission links.
Despite these teachings of the art, however, no viable house arrest monitoring system has yet been developed to applicant's knowledge. This is because there are numerous features that must be present in a viable house arrest monitoring system that are lacking in the teachings of the prior art. For example, it is desirable to have the electronic tag or other device that identifies the individual being monitored (usually some sort of transponding device) to be worn at a location that is not readily visible to the casual observer and at a location where it cannot be removed by its wearer, but at a location where it will not unduly interfere with the activities of its wearer. This requirement can be met if the tag is worn on an ankle, thereby allowing the tag to be readily concealed by the clothes (pants leg and/or sock) of its wearer. However, such use causes the tag to be located very close to the ground, or floor level. When the floor level comprises earth or concrete, as is often the case, some significant transmission problems can result. This is because the RF signal, by necessity a fairly weak signal that is generated for a limited transmission range from a limited energy source, is either absorbed in, or otherwise destructively reflected from the earth or concrete surface. Further, concrete is often heavily laced with reinforced steel, which also tends to interfere with reliable low-energy RF transmissions. Moreover, the walls of the structure whereat the house arrest is being performed may have wire mesh or other metal objects therein that destructively interfere with the transmission of low-energy RF signals.
Simply increasing the energy of the RF signals transmitted from the tag is generally not a viable solution to this problem. In the first place, the tag only has a limited energy source, and it is desirable to have this energy source last for as long as possible. In fact, in accordance with the teachings of the invention herein, the limited energy source (a battery) should be permanently sealed in the tag so that the wearer of the tag has no access thereto. In the second place, higher energy RF signals create numerous other problems for those in the vicinity of the transmission, and as such, must be carefully regulated by the FCC or other regulatory agencies.
A further feature that desirably exists in a viable house arrest monitoring system is that readily noticeable or visible antennas or antenna arrays not be used. Such antennas immediately draw attention to the fact that a house arrest situation exists. Accordingly, the antennas that are used should be of the low profile variety that readily blend into the surroundings of a typical house environment. Further, such antenna(s) and related circuitry must be able to reliably pick up or sense the desired signal and discriminate against destructive reflections or external signals that may be present within the house-arrest structure.
Still a further feature that is of critical importance to the successful use of a house arrest system is the integrity of the system. That is, all components of the system at the house-arrest location must be able to sense and signal the occurrence of any attempts to tamper therewith. Further, while there is nothing that can absolutely prevent the destruction of the system's components at the house arrest location, it is desirable that such destruction or attempted destruction be promptly communicated to a central processing location so that appropriate follow up action can be performed. Most importantly, the electronic identification (ID) tag that is worn by the person under house arrest must not be removable. At a minimum, any attempts to remove the tag should be detectable.